A Japanese teenager who allegedly killed his mother and chopped her body into pieces has told police he simply did not like her, and wanted to know more about dissection, reports have said.

A Japanese teenager who allegedly killed his mother and chopped her body into pieces has told police he simply did not like her, and wanted to know more about dissection, reports have said.

The 19-year-old allegedly dismembered his mother's body in the bathroom, cutting her into at least 15 pieces using kitchen knives, the Sankei daily said on Saturday, citing unnamed police sources.

The teenager, who lived with his mother in a small apartment near Tokyo, then kept the body parts in the bathtub, which he filled with water, before starting to dump it piece by piece in plastic bags, the report said.

He told police he "didn't like her" and she was an "ordinary person", the Sankei reported, quoting an unnamed investigator.

He also said he was interested in the dissection of a human body, the Yomiuri and Mainichi newspapers reported.

The suspect, who has not been named as he is still a minor under Japanese law, was arrested on March 14 after a relative visited the apartment and found some of the body parts.

The murder is believed to have been committed about two weeks previously.